Honing devices have long been and are still extensively utilized for finishing interior cylindrical walls, such as cylinder walls of internal combustion engines. Such devices typically employ a rotary body having several circumferentially-spaced slots formed radially thereof, which slots mount therein axially elongated abrasive honing elements. These honing elements are typically expanded radially outwardly of the body for contact with the cylinder wall by an actuator which, while it may assume many conventional forms, typically comprises a cone movable axially of the rotary body. Honing devices of this type are well known, and reference is made to U.S. Pat, Nos. 1,846,371, 1,982,836, 2,263,781, 3,154,893, 3,216,155, 3,645,050 and 3,861,091 which illustrate various such devices.
The conventional honing device has, for many years, employed a plurality of abrasive tools and wood guides disposed in circumferentially spaced relationship around the body so that both the tools and guides rubbingly engage the cylindrical wall. The device typically employs at least a pair of abrasive tools and a pair of guides, the tools and guides being conventionally positioned diametrically opposite one another and circumferentially alternately spaced so that the tools are hence disposed at substantially 180.degree. intervals, the guides are similarly disposed at substantially 180.degree. intervals, and the guides and tools are spaced approximately at 90.degree. intervals. Arrangements of this general type are illustrated by U.S. Pat. Nos. 1,846,371, 1,982,836, 2,263,781 and 3,645,050. With arrangements of this latter type, it has been observed that use of at least one pair of guides is necessary, particularly when using only a pair of abrasive tools, to minimize vibration, noise and chatter.
In an attempt to increase the honing rate, others have attempted to eliminate the guides and increase the number of circumferentially-spaced abrasive tools. In some instance the number of tools has been dramatically increased. Examples of such structures are illustrated by U.S. Pat. Nos. 3,154,893 and 3,861,091. With such arrangements, however, it has been discovered that the increased contact area between the abrasive tools and the cylinder wall appears to increase the harmonic vibrations created during the honing operation, whereby noise and chatter increases and the quality of finish decreases, and hence such devices have normally proved less than desirable.
In an attempt to improve upon the noise and chatter characteristics associated with the typical honing device employing a diametrically opposed pair of stones (i.e. tools) and an intermediate diametrically opposed pair of guides, there has also been developed a honing device wherein the stones and guides are nonsymmetrically positioned. In this known device, as illustrated by U.S. Pat. No. 3,216,155, both the stones and guides are nonsymmetrically related, and in fact the stones are both disposed within one diametric half of the body, and both guides are disposed in the opposite diametrical half of the body. This arrangement, however, still employs large abrasive stones and separate guides for rubbing contact with the cylindrical wall and hence does not optimize finishing of the wall.
In the conventional honing devices, it has been a standard practice to utilize abrasive stones having a width (as measured in the direction of rotation) which is typically a minimum of about 3/8 inch to 1/2 inch. It has generally been believed that stones of substantial widths are required to permit effective finishing (i.e., honing) of the cylindrical wall. Further, these widths have been utilized so as to avoid cracking of the axially-elongated abrasive strips which define the stones. Such stones, however, are believed by Applicants to have been detrimental to the honing process in that they have increased the contact area, causing a corresponding increase in noise and chatter, and generation of substantial heat. Such stones have also generally resulted in increased use of greater contact pressure between the wall and stone so that the abrasive has been observed to crush and wear rapidly, and hence is unable to carry out an effective finishing operation.
In addition, conventional honing devices have typically required that the cylindrical wall be honed or finished using a two-step process. Initially, a rough finishing step is carried out utilizing abrasive elements of rather course grit, such as 150 to about 180 grit. Thereafter, the honing device must be removed from the cylinder and the course-grit abrasive elements removed and replaced with fine-grit elements, such as in the order of about 240 to 320 grit. The device is then reinserted into the cylinder and additional finishing carried out so as to provide the desired smooth finish on the cylindrical wall. Needless to say, this two-step process is undesirably labor intensive and time consuming, but nevertheless has been typically utilized in order to provide the cylinder wall with the desired finish.
Further, abrasive elements of fine grit are substantially more costly than abrasive elements of course grit, and hence users attempt to minimize the extent of use of fine grit stones due to the significant cost thereof.
Accordingly, it is an object of this invention to provide an improved abrasive honing element for use in conjunction with a honing device so as to overcome many of the disadvantages associated with prior art devices of this general type.
More specifically, it is an object of this invention to provide an improved honing tool for use on a honing device which employs a plurality of radially-displaceable tools mounted circumferentially around a rotary body, which tools are each preferably constructed as a laminate formed by the axially elongated abrasive strip bonded to a backing strip, the latter preferably being of wood. The abrasive strip has a width (as measured in the direction of rotation) which is relatively small and generally significantly less than the width of the backing strip, and both the abrasive and backing strips are radially urged for simultaneous contact with the cylinder wall which is being honed.
In a preferred embodiment, the honing device is normally provided with at least two pairs of said tools mounted circumferentially therearound, with the tools of each circumferentially-adjacent pair being reversely circumferentially oriented so that the abrasive strips on each adjacent pair of tools are reversely circumferentially oriented. The tools are preferably mounted such that the abrasive strips as located circumferentially around the body are disposed in a nonsymmetric or nonuniform arrangement, this preferably being achieved by mounting the plurality of tools uniformly angularly around the body so that the reverse circumferential orientation of the tools hence results in the abrasive strips being nonuniformly angularly spaced.
The improved tool of this invention, as utilized in a honing device, such as described above, preferably employs an abrasive strip having a width of about 1/8 inch, which width is significantly smaller than that typically utilized in the honing industry, and the backing strip of wood preferably has a width which is greater than the width of the abrasive strip. This hence provides proper strength and backing for the thin abrasive strip, and at the same time permits the abrasive strip to be radially urged against the cylinder wall with significantly high contact pressures if desired. At the same time, the tool of the present invention results in the face of the wood backing strip also being pressed against the cylinder wall simultaneous with the face of the abrasive strip so that both the abrasive and wood faces effectively perform a finishing operation.
Initial experimental evaluation indicates that this invention enables the use of lower contact pressure between the tool and the cylinder wall in conjunction with the use of a stone of large grit in the order of 150 to 180 grit size, while still enabling the honing operation to be carried out at a more rapid rate and providing a finish of high quality which is more comparable to a finish which could previously be achieved only by utilizing a stone of high grit such as in the order of at least about 240. It is believed that the improved tool of this invention is able to achieve this highly desirable result inasmuch as the contact of the wood face against the cylinder wall directly adjacent the abrasive face provides a much more uniform distribution of pressure throughout the contact area, and at the same time significantly minimizes vibration and chatter directly at the contact area. Further, this also provides better control over the wear and penetration of the abrasive face into the cylinder wall so that the larger grit can more effectively perform a cutting action so as to effect material removal. It is believed that this improved cutting action is due to the fact that the large grits remain bonded to the stone, rather than being broken from the stone as in conventional tools, whereupon the grit gradually wears down to a smaller size so as to create a finer finish on the cylinder wall. The wood face also appears to significantly assist the cutting action by effecting a smoother finishing or polishing so that the resultant cylindrical wall is hence of smooth finish, and in fact is of a much higher degree of smoothness than would otherwise be obtainable using an abrasive strip of such large grit. In fact, it has been observed that the desired quality finish can be achieved using the tool of this invention, employing a strip of large size grit, while performing only a one-step finishing operation, in contrast to the required two-step process required by prior art devices.
Hence, the improved tool and honing device of this invention is believed to represent a significant improvement in the honing art since it permits the use of a coarser grit for the complete finishing operation so as to provide economy of material, it permits the finishing to be carried out at a higher speed which is typically accomplished solely when using coarse grit but at the same time provides a finish which could previously be accomplished solely using fine grit, it permits the finishing to be accomplished using a lower contact pressure so as to minimize wear of the honing device, it provides greater life for the tools since the grit appears to permit the desired finishing to be accomplished by a true cutting action rather than a crushing of the grit, it permits the use of a stone requiring less quantity of expensive abrasive and bonding agent, and it permits the overall finishing operation to be accomplished in a significantly more efficient manner which is both less time consuming and less labor intensive since the finishing operation can be effectively accomplished in one-step rather than two-steps as normally previously required.
In a variation of the improved tool of this invention, an abrasive strip is bonded to both sides of the wood backing strip. The total width of the two abrasive strips is less than the width of the wood strip. This tool is preferred for use on honing devices using a large number of tools, such as power-driven devices employing six or more tools.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.